[PATCH] D62786: [X86] X86DAGToDAGISel::matchBitExtract(): pattern a: truncation awareness

Roman Lebedev via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Sat Jun 1 16:30:13 PDT 2019

lebedev.ri created this revision.
lebedev.ri added reviewers: craig.topper, RKSimon, spatel.
lebedev.ri added a project: LLVM.

Finally tying up loose ends here.

The problem is quite simple:
If we have pattern `(x >> start) &  (1 << nbits) - 1`,
and then truncate the result, that truncation will be propagated upwards,
into the `and`. And that isn't currently handled.

I'm only fixing pattern `a` here,
the same fix will be needed for patterns `b`/`c` too.

I *think* this isn't missing any extra legality checks,
since we only look past truncations. Similary, i don't think
we can get any other truncation there other than i64->i32.




-------------- next part --------------
A non-text attachment was scrubbed...
Name: D62786.202571.patch
Type: text/x-patch
Size: 4879 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190601/0325faf8/attachment.bin>

More information about the llvm-commits mailing list